247 lines
11 KiB
Plaintext
247 lines
11 KiB
Plaintext
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Dialing Plan (16 May 1990)
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1. Area Codes, North America
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Bell Communications Research (Bellcore) is the organisation responsible
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for the maintenance of the area codes and the dialing setup for
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North America since the breakup of AT&T several years back. This
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group sets standards for dialing, telephone number format, etc.
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Area codes (or Numbering Plan Areas (NPA)) in North America are presently
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of the form NZX where N represents a number from 2 to 8, Z is 0 or 1 and
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X is any number. This distinguishes area codes from central office (exchange)
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codes which are usually of the form NNX (ie. the difference between an
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exchange and an area code is usually in the second digit, whether or not
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it is a 0 or 1).
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Area codes ending in -11 are not used, as they are normally used for special
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services. The special purposes generally reserved are:
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411 directory assistance
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611 repair
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811 business office
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911 emergency
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The other N11 codes are sometimes used within specific localities for
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special purposes (711 is used for mobile service in British Columbia,
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in the form 0+711)). In some cases, services are accessed through the
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long distance network (ie. 1+411 or 1+611).
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Area codes ending in -10 have been TWX numbers (teletype service).
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TWX area codes include 510, 610, 710, 810 and 910. Normal telephone
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numbers do not (yet) use area codes ending in -10, though these codes
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will be reassigned to regular telephone service as TWX is eliminated.
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Upcoming examples of this are the area code splits of 213 (Los Angeles
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adds area code 310) and 415 (San Francisco adds area code 510).
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Area codes ending in -00 are usually reserved for special services
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like 700, 800 or 900. In fact, these codes are not considered to be
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area codes as such, but Service Access Codes (SACs).
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(2) Dialing Codes...
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Theoretical capacity of the telephone system:
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The original design of telephone numbers was:
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(NZX) NNX XXXX
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In theory, this gives:
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N Z X N N X X X X X
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8 * 2 * 10 * 8 * 8 * 10 * 10 * 10 * 10 * 10 = 1.024 billion numbers
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However, as some area codes and exchanges are reserved for special
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purposes (such as 411, 555 exchange, etc), the total possible number
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of telephone numbers will be somewhat less.
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As the exchange codes in some area codes were used up, some central offices
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started using the NXX format, where the middle digit can then be a 0 or 1;
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examples of these may be found in New York City or Los Angeles. The March
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1990 conversion of the (416) area code around Toronto is another example,
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as is a similar change to North Carolina's dialing around the same time.
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The dialing is changed so that dialing 1+ a number always requires an area
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code, and in the case of (416), will mean that 1+416+ will be needed for
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long distance calls within (416). In New York City, however, all calls
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within an area code are dialed with seven digits only (without dialing
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1 first, let alone the area code).
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Now, telephone numbers look like this:
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(NZX) NXX XXXX
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This gives a potential of:
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N Z X N X X X X X X
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8 * 2 * 10 * 8 * 10 * 10 * 10 * 10 * 10 * 10 = 1.28 billion numbers
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However, codes like 411 and 611 would not be assigned because they will
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still be needed for services such as directory assistance and repair.
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Nevertheless, some unused N11 codes like 211 may be found in some area
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codes as active exchanges. It's also not a good idea to assign the home
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area code (could cause confusion).
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Going from NNX exchange codes to NXX only represents a 25% increase in the
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total theoretical amount of telephone numbers, and not all area code regions
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are expected to run out of exchanges. Also, area codes do not generally go
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outside a state or provincial boundary (the only exceptions are in Canada,
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where 902 serves both Nova Scotia and Prince Edward Island, area 819 which
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covers the eastern Northwest Territories as well as part of Quebec, and
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area 403 which covers Alberta, Yukon and the western Northwest Territories).
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The ultimate goal is not only to use area codes for exchanges codes, but
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to use exchanges codes for area codes also. This means that telephone
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numbers will ultimately look like this:
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(NXX) NXX XXXX
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This gives a potential of:
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N X X N X X X X X X
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8 * 10 * 10 * 8 * 10 * 10 * 10 * 10 * 10 * 10 = 6.4 billion numbers
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With a five-fold increase in the number of possible area codes, there
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should be plenty of room to grow for some time.
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(3) Dialing Codes...
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Basically, all calls within an area code will ultimately be dialed in
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one of the following ways 1) dial seven digits, 2) dial 1 + home area
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code + number, or 3) dial 1 + seven digit number within area code, then
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wait for a few seconds to time out. One alternative not mentioned in
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official documents (for touch tone phones) is to use 1 + seven digit
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number in home area code + '#' with the # key terminating the dialing.
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The initial set of new area codes will take the form NN0, or those numbers
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ending in '0'. This means that areas codes that do not have exchanges
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ending in '0' (or only a few NN0 exchanges that could be renumbered)
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can still be able to tell the difference between an exchange and an
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area code by looking at the first three digits.
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The new NN0-type area codes will be assigned starting with these
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first few codes (in order):
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260, 480, 520, 590, 650, 220, 250, 490, 660, 680, 720, 730, 850, 940 ...
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970 will be reserved for phone testing purposes, and is not slated to
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become an area code.
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All telephone systems are expected to change their systems over to allow
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for the new style of area codes by 1 July 1995, or perhaps earlier. This
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could mean that other area codes will be required to dial the area code
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for long distance calls within area, even though the area code is not
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running out of exchanges itself (eg. areas 519, 705).
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Dialing Scheme
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* 1 + will generally be used for direct-dialed long distance calls within
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North America, especially calls outside the local area code.
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* 0 + is used to dial operator-assisted or automated credit card calls within
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North America. After 0 + (area code) + number are dialed, a prompt tone
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(same tones as a dial tone, but for a very short duration) will be issued,
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then one of the following actions will be taken:
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1) wait for a few seconds, then an operator will come on line
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2) dial '0' to get the operator immediately (for a collect, person to
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person call, etc)
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3) dial the telephone company credit card number for billing
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It is unclear what will happen in the cases of automated collect calls,
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as to what kinds of dialing would be standard in that case.
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(4) Dialing Codes...
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Dialing 0 and waiting will get the local area operator.
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* 00 is used in the U.S. to get the operator for a default long distance
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carrier. This is used as most long distance companies have their own
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operators. A single 0 digit will call up the local operator (with the local
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telephone company as opposed to the long distance company).
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It's important to note that the U.S. is broken up into LATAs (Local Access
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Transport Areas), and long distance calls are treated differently whether
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they are made within a LATA, or if a call is placed to another LATA. Thus,
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there could be an operator for within the LATA (intra-LATA calling) and an
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operator for inter-LATA calling (from a long distance carrier).
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* 01 is used for overseas calls. 01 + indicates an operator-assisted or
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automatic credit card call, while 011 + indicates a direct-dialed overseas
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call. 010 is reserved for some unspecified future use.
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* 10XXX + is used in the U.S. to indicate which long distance carrier to use
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in a situation known as "equal access". This allows a telephone subscriber
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to select a long distance company for a particular call. For instance,
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10288+ gets AT&T while 10222+ gets MCI and 10333+ US Sprint. After this
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code, a 1 or 0 is dialed (to indicate direct dial or operator-assisted call)
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then the number to be called.
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The codes 10000 is not available for assignment
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10001 - 10099 are reserved for restricted purposes
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10100 - 10199 are reserved for international carriers
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(note that because of possible dialing mistakes that may
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confuse some codes with 01- overseas dialing codes,
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10100-10119 are to be assigned after all 10120-10199 codes
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are assigned.)
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10200 - 10999 are assigned to standard long distance carriers
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A list of the U.S. long distance carriers and their 10XXX+ codes is listed
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in a separate document.
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Canada doesn't have to worry about this code quite yet, depending on the
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results of the CNCP/Rogers intention to provide alternate long distance
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service.
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* 11- or '*'- (tone dialing) is reserved for special calling services like
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call waiting functions, etc. For instance, 1170 is used to disable the
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call waiting, like *70 can be used on touch tone phones. The current
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special calling codes on many local telephone systems are:
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*57 or 1157 - call tracing request (some systems use this for call back)
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*60 or 1160 - call blocking activated
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*61 or 1161 - priority ring activated
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*63 or 1163 - select call forwarding activated
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*66 or 1166 - repeat dialing activated
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*67 or 1167 - call number ID blocking (done for each call)
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*69 or 1169 - call return activated
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*70 or 1170 - disable call waiting
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*71 or 1171 - 3 way calling according to usage
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*72 or 1172 - enable call forwarding
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*73 or 1173 - disable call forwarding
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*74 or 1174 - modify speed calling directory entry (for 8 number service)
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*75 or 1175 - modify speed calling directory entry (for 30 number service)
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*76 or 1176 - call pickup
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*79 or 1179 - ring again
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*80 or 1180 - call blocking disabled
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*81 or 1181 - priority ring disabled
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*83 or 1183 - select call forwarding activated
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*86 or 1186 - repeat dialing disabled
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*89 or 1189 - call return disabled
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(5) Dialing Codes...
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2. Reserved exchanges
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Each area code will have certain exchanges set aside for special purposes.
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These exchanges are:
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555 - directory assistance
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950 - used to access other long distance services (U.S.)
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958, 959 - reserved for phone tests
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976 - special recordings, private services
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844 and 936 have been reserved for time and weather services, but this
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is not widely adhered to. In area code 416, these exchanges are for
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Oakville and Tottenham respectively. These services will likely be
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incorporated into 976 service, or into other exchanges.
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Other Information
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A file with the Tel Docs (TELDOC) package, GUIDECOD.DOC, explains in more
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detail the 700, 800 and 900 area codes, with lists of exchange/carrier
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assignments and other details. This file should be included in the Tel
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Docs package. This is the same document as the Guide prepared by TELECOM
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Digest, an electronic conference regarding telephone/telecommunication
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matters.
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